Long-chain unsaturated dicarboxylic acids and esters thereof



United States Patent LONG-CHAIN UNSATURATED DICARBOXYLIC ACIDS .AND ESTERS THEREOF Donald Drake Cofiman, West Chester, Pa., and Harry Norman Cripps, Wilmington, Del., assignors to E. L du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application January 14, 1953, Serial No. 331,302

Claims. (Cl. 260-537) This invention relates to long-chain organic compounds and, more particularly, to a process of preparing same. Still more particularly, the invention relates to long-chain unsaturated alpha, omega-dicarboxylic acids and their esters, and to the preparation of these compounds. This application is a continuation-inpart of applicants U. 5. application Serial No. 266,115, filed January 11, 1952, and now abandoned.

Long-chain organic compounds are useful in a wide variety of applications. Long-chain difunctional compounds are particularly useful in the preparation of con densation polymers and plasticizers, and as intermediates in various chemical reactions. They can be prepared by a number of methods. However, the heretofore "known methods of preparing these long c'hain compounds are not satisfactory for the preparation of some symmetrical long ch'ain di functional organic compounds which are especially desirable, and, consequently, a new and Sim roved process for. preparing them :is of considerable practical importance. I

' A-n obiec'tof the present inventionis to provide 'a new process of preparing long-chain saturated and' unsaturated organic compounds. Another "object is 'to provide a new process of preparing long-chain diflm'ctional organic :compounds. it further object is to :provide a new class iof long-chain unsaturated 'alpha,omega-dicarboxylic acids and their esters.- Other obiedts will be apparent from the description of the invention given hereinafter.

The above objects are accomplished according to the present invention :by contacting a polymerizable l,3-con ju'gated :diene' or :monoethylenically unsaturated aliphatic ester with a ketone peroxide in the presence of a redox reducing agent, in a solvent for the reactants, the molar ratio of the dien'e or aliphatic ester to'theketone *peroxide being not more thanfi to .l and the ketonejperoxide being a peroxide of 'a cyclic ketone, ketoester or acyclic 'diketone. In a more specific embodiment, the invention comprises the preparation of long-chain unsaturated alpha, omega-dicarboxylic acids by contacting a 1,3'-:eorljugated diene with a ketone peroxide, preferably a peroxide of a cyclic ketone, in .the presence of a :redox reducing agent, in a solventfor the reactants, in tion of l-S f'mole's iif diene per mole of .keton'e'tperoxide. 1 invention further comprises, as a new class of compounds, those long chain unsaturated alpha,omegadicarboxylic-acids :having :two -nonc'oifiugated tethyleni'c The group lt iltRa) the formula above include s 'ih e a propor- Patented Oct. 29, 1957 two possible radicals derived from the specific diene selected. For example, the use of butadiene leads to the formation of three isomers:

I. V H O O CR'-CHr-CH=CHCHr-C.Hr-C H=CHO EFF/0'0 OH A preferred way of carrying out the process of this invention involves contacting one to five moles of a 1,3- conjugated diene, e. g., 1,3-butadiene, with one. mole of a ketone peroxide which is a peroxide of a cyclic ketone, ketoester or acyclic diketone, e. 'g.,.cyclohexanone peroxide, or the peroxides'of ethyl acetoacetate, acetonylacetone, and the like, in the presence of one mole of a redox reducing agent, i. e., one of the reducing agents commonly used in the redox art, such as ferrous sulfate, in a solvent for the reactants. Preferably, a solution of the ketone peroxide, a second solution containing a stoichiometrically equivalent amount of the reducing agent, and a third solution of the major proportion of the conjugated diene are added gradually and simultaneously III.

with thorough agitationto a solution of a small portion of the diene.

The long-chain compounds obtained by the process of this invention are isolated from the reaction mixture by conventional methods. A generally satisfactory way consists in removing excess volatile reactants by evaporation and then, if an aqueous reaction medium has been employed, extractingthe reaction mixture with an organic solvent, e. g., diethyl ether, to separate'the product from the aqueous layer. The organic layer can then "be dried and fractionally distilled. If the product is a long-chain discarboxylic acid, the type of product formed from certain ketone peroxides, the extract can be treated with diluteaqueous alkali and the acqueous alkaline :layerrcontaining the salt of the dicarboxylic acid then acidified. The free acid precipitates from this mixture and is separated from the organic layer by filtration. It is then purified by crystallization from an organic solvent such as pe'troleum'ether or ethyl acetate.

The following examples illustrate specific embodiments of this invention.

Example I A mixture of 100 ml. of distilled water and 100 ml. of reagent grade methanol is placed in a one literreaction vessel equipped with aJhigh speed stirrer, a con denser cooled by solid carbon dioxide, threecalibrated addition funnels, and a thermometer. The mixture is cooled to 20 'C., and 20 ml. of liquefied 1,3-butadiene is added slowly. Solutions of 66 g. of cyclohexanone peroxide in methanol (total volume 300 ml.) and 139 g. of reagent grade water (total volume 300 ml.) are added at equal rates over approximately45 minutes with rapid stirring while the temperature is imaintained at -20 C. i5 C.

' Simultaneously with theseiadditions, '60 ml. of liquefied l,3-.butadiene is added at such a rate that this addition is complete at the same time as the cyclohexanone peroxide and ferrous :sulfate solution additions are completed. After allth'e reactants are "added, the mixture is stirred for another 10 minutes to complete the reaction.

. mixture warms to room temperature.

The condenser isremoved from the reaction vessel and excess butadiene is allowed to escape as the reaction The resulting crude product is extracted from the aqueous layer with ferrous sulfate heptahydrate in distilled four 100 ml. portions of diethyl ether. The ether solution is stirred with 150 ml. of aqueous sodium hydroxide, and the aqueous layer is separated. Acidification of the alkaline layer results. in a suspension of a solid in an oily substance which is separated from the aqueous layer. Filtration yields 24 g. of a Waxy solid. This solid is purified by boiling in petroleum ether, decanting the clear solution from the oily residue, and chilling the clear solution in solid carbon dioxide. A white powder precipitates. This solid has a melting point of 108l12 C. This product comprises in major proportion 7,1l-octadecadiene-l,18-dicarboxylic acid but also contains some material having terminal carbon-carbon unsaturation as judged by the infrared spectra.

Analysis calculated for (2201 13404! C,'71.1%; H, 10.1%; neutral equivalent 169.2. Found: C, 70.6%; H, 10.1%; neutral equivalent 168.3.

This acid forms a di(p-bromophenacyl) ester melting at 116-118 C.

Analysis calculated for CzsHuOsBr: C, 59.0%; H, 6.4%; Br, 21.5%. Found: C, 58.96%, 58.71%; H, 6.26%, 6.02%; Br, 22.10%, 22.29%.

There are also isolated from the reaction mixture of this example two other fractions. The first of these is an acidic oil believed to be a polybutadiene of low molecular weight terminated by carboxypentyl groups. The neutral equivalent, 229.4 and molecular weight, 580- 625, indicate that an average of 46 butadiene groups are present. The second of these fractions is a mixture of neutral compounds which can be separated into cyclohexanone and an unidentified neutral unsaturated compound.

Example 11 The process of Example I is repeated with the exception that 64 g. of chloroprene (2-chloro-1,3-butadiene) is substituted for the 1,3-butadiene. There is isolated from the reaction mixture by the procedure of Example I 45 g. of an unsaturated acidic oil. Esterification of this oil with methanol in the presence of sulfuric acid yields an ester product from which about 1 g. boiling at 140-141 C./0.3 mm. is obtained. Analysis indicates this fraction to be thedimethyl ester of a chloroprene dimer having carboxypentyl end groups.

Analysis calculated for CzzHasOrClz: C, 60.7%; H, 8.30%; sap. No. 207.7. Found: C, 58.30%, 58.20%, 58.29%; H, 8.41%, 8.46%, 8.40%; sap. No. 203.8, 199.9.

Example III The process of Example I is repeated with the single exception that 33 g. of cyclopentadiene is substituted for the 1,3-butadiene. On working up the reaction mixture as in the previous examples, there is isolated 26 g. of a brown acidic oil.

Example IV 4 Example V Following the general procedure of Example I, a solution of 45 ml. of liquefied 1,3-butacliene in 100 ml. of nitrogen-saturated methanol is cooled to C. in an atmosphere of nitrogen. An aqueous ferrous sulfate heptahydrate solution (112 ml. of a 1.67 M solution in nitrogen-saturated distilled water) and 38.8 g. (0.186 mole) of hydroxydicarbethoxymethyl hydroperoxide (prepared from ethyl oxomalonate in anhydrous ether) are added simultaneously with vigorous agitation over a 3- minute period. After adding 100 ml. of distilled water, the excess of 1,3-butadiene is allowed to escape from the reaction flask as the mixture is warmed to room temperature. The reaction mixture is extracted with 150 ml. of diethyl ether and the ether extract is washed with 50 ml. of a 10% aqueous sodium bicarbonate solution. After drying with 5 g. of anhydrous magnesium sulfate, the ether solution is distilled to remove the ether and to obtain a pale yellow residue, A, which weighs 17.5 g. A portion of this residue is distilled through a onefoot fractionating column packed with platinum gauze. After removal of 1.4 g. of low boiling material, there are obtained 4.3 g. of material boiling at 160169 C./11 mm., refractive index, 11 of 1.4541 (fraction 2), and 4.4 g. of material boiling at 170179 C./11 mm., n 1.4549 (fraction 3), and 2.1 g. of higher boiling material having a refractive index of 1.4401. Analysis indicates fraction 2 to be the diethyl ester of a butadiene dimer having carboxyl end groups.

Analysis calculated for C14Hz204: C, 66.3%; H, 8.4%; sap. No. 127; iodine No. 199.5. Found: C, 64.22, 63.70, 64.25%; H, 8.53, 8.48, 8.59; sap. No. 120.9; 117.3; iodine No. 179, 179.

A mixture of 1.07 g. of fraction 3 and 25 ml. of 10% aqueous sodium hydroxide is refluxed for 4 hours under nitrogen atmosphere. Acidification of the pale yellow solution with concentrated hydrochloric acid gives 0.35 g. of a tan solid. Analysis indicates this product to be a decadienedioic acid.

Analysis calculated for C10H1404: neut. eq., 97.1. Found: neut. eq., 99.8.

A solution of 2.5 g. of the crude yellow residue A of Example V is dissolved in ml. of absolute ethyl alcohol and is hydrogenated at 30-40 lb./sq. in. pressure using 0.1 g. of platinum oxide as catalyst. After filtration of the reaction mixture through a Celite mat, the hydrogenated mixture is refluxed for 8 hours with a solution of 3 g. of sodium hydroxide in ml. of distilled water. The black solution obtained is diluted with 15 ml. of distilled water and is treated with two 1 g. portions of decolorizing carbon. Acidification of the alkaline solution yields 1.76 g. of a solid acid. On recrystallization from 100 ml. of distilled water in the presence of decolorizing carbon there are obtained 0.67 g. of white crystals of sebacic acid, M. P. 130.5-132 C. A mixture of this acid with an authentic example of sebacic acid melts at 132-134 C.

drogenated oil which is treated with methanol and sul- I furic acid to give 41.3 g. of the dimethyl ester. On distillation there is isolated 9.8 g. of a yellow oil boiling at 170-199 C. at 0.3-0.4 mm. A major proportion of this product comprises dimethyl 7,12-dimethyl-7,11- octadecadiene-l,IS-dicarboxylate.

Analysis calculated for C24H4s-O4: C, 72.4%; H,.11.6%; neutral equivalent 199.3. Found: C, 71.16%, 70.90%; H, 11.35%, 11.35%; neutral equivalent 205.8, 206.3", refractive index n =1.4549.

Analysis calculated for C10H1s04: neut. eq., 101.1. Found: neut. eq., 102.8, 103.0.

From these results it is clearly evident that the reaction products of hydroxydicarbethoxymethyl hydroperoxide, ferrous ion and 1,3-butadiene are butadiene dimers having carbethoxymethyl end groups and that one of the components of this mixture is diethyl 3,7-decadiene-1,10-dioate.

Example VI is reacted under the conditions described in Example V.

Isolation of the reaction product in the same manner yields 18.6 g. of a fragrant yellow oil. On distillation of this yellow oil through a 6-inch column, there are obtained 4.11 g. of unreacted ethyl acetoacetate (from the preparation of the ketone peroxide), 4.4 g. of intermediate fraction boiling from 75 C. to 131 C./0.7 mm., and 5.15 g. of product boiling at 131-135" C./0.7 mm. having a refractive index, "D25, of 1.4560. Analysis indicates this fraction to be the diethyl ester of a butadiene dimer having carboxymethyl end groups.

Analysis calculated for C16H26041 C, 68.05%; H, 9.30%; sap. No., 141.2; quantitative hydrogenation, 0.0142 g. hydrogen/g. of sample. Found: C, 68.16, 67.48, 67.66%; H, 9.28, 9.38, 9.28%; sap No., 143.6, 143.6; quantitative hydrogenation, 0.018, 0.017 g. hydrogen/g. sample.

A 3.80 g. sample of the above unsaturated ester yields on saponification with 1.5 g. of sodium hydroxide dissolved in 25 ml. of distilled water, 2.5 g. of a crude solid acid. Recrystallization of 2 got the crude acid from 25 ml. of distilled water and ml. of dioxane yields 1.5 g. of a pure solid acid melting at 159.5-160.5 C. This is a dodecadienedioic acid.

Analysis calculated for C12H1a04: C, 63.69%; H, 8.03; neut. eq., 113.1; quantitative hydrogenation, 0.0177 g. hydrogen/g. of sample. Found: C, 63.92, 93.84%; H, 8.00%; neut. eq., 110.2, 110.0; quantitative hydrogenation, 0.0193 g. hydrogen/g. sample.

A 4.03 g. sample of the 16-carbon unsaturated ester of this example dissolved in 25 ml. of absolute ethyl alcohol absorbs hydrogen in amount corresponding to a pressure drop of 2.5 lb./sq. in. when shaken at 30-40 lb./sq. in. hydrogen pressure with 0.15 g. of platinum oxide catalyst. Theoretical absorption corresponds to a pressure drop of 2.3 lb./sq. in. of hydrogen. Saponification and acidification of the filtered hydrogenation mixture thus obtained yields 2.09 g. of a crude saturated 12- carbon dicarboxylic acid. Recrystallization from 1 l. of water gives 1.0 g. of white needles of 1,12-dodecanedioic acid, M. P. 127.5-1285" C. There is no depression in melting point when a sample of this acid is mixed with an authentic sample of 1,12-dodecanedioic acid.

Analysis calculated for 0121-12204! neut. eq., 115.1. Found: neut. eq., 113.8, 111.0.

Example V Il A mixture of 55.1 g. of ethyl levulinate and 48.0 g. of 27.9% aqueous hydrogen peroxide, and a solution of 107.0 g. of ferrous sulfate heptahydrate in nitrogensaturated distilled Water (total volume 100 ml.) are added separately and simultaneously with vigorous stirring at C. to 10 C. over a period of four minutes to a solution of 110 ml. of liquid 1,3-butadiene in 100 ml. of nitrogen-saturated methanol. There is obtained 44.6 g. of crude neutral product which, on distillation, yields 32.8 g. of recovered ethyl levulinate and 9.6 g. of a higher boiling residue. This residue contains in major proportion the diethyl 5,9-tetradecadiene-1,14- dioate. This residue is dissolved in ethanol and is hydrogenated at 30-40 lb./sq. in. hydrogen pressure, using platinum oxide catalyst. saponification of the resultant hydrogenated mixture yields 4.5 g. of crude 1,14-tetradecanedioic acid, M. P. 123-125" C. After two recrystallizations from ethyl acetate, the acid melts at 125- 126 C. The melting point of this acid as recorded in the literature (Helv. Chim. Acta. 9, 264 (1926)) is Analysis calculated for C14Hz604: neut. eq., 129.2. Found: neut. eq., 132.0.

Example VIII A mixture of 57.14 g. of acetonylacetone and an equivalent amount of aqueous 27% hydrogen peroxide (63.0 'g.), a solution of 139 g. of ferrous sulfate heptahydrate in nitrogen-saturated distilled'water (total volume 200 m1), and a solution of'94 g. of liquid 1,3-butadiene' in 150 ml.

of nitrogen-saturated methanol are reacted under the conditions described in Example VII. The reaction mixture is extracted with ether to separate the organic materials from the ferric salts and, after evaporation of the ether from the organic fraction, there is obtained 25 g. of a colorless liquid. This product is combined with a similar product obtained in another run carried out under the same conditions. From 41.5 g. of combined product there are obtained by distillation 6.5 g. of recovered acetonylacetone; 4.7 g. of intermediate fractions boiling from 130 C./0.5 mm. to 139 C./ 0.55 mm.; fraction 4, 4.9 g., boiling at 145 C./ 0.55 mm., n 1.4728; fraction 5, 5.1 g., boiling at 145-150" C./0.550.58 mm., n 1.4700; and fraction 6, 2 g., boiling at l52-154 C./0.58 mm., which is a solid. Analyses indicate that fractions 4, 5, and 6 are 16-carbon diketones consisting of butadiene dimers having 3-ketobutyl end groups.

A solution of 4.19 g. of fraction 5 in 25 ml. of absolute ethyl alcohol is hydrogenated at 30-40 lb./ sq. in. pressure, using 0.1 g. of platinum oxide catalyst. After removal of catalyst, the ethanol is evaporated to obtain a residue which is a white solid. This solid is recrystallized from a mixture of 15 ml. of ethyl alcohol and 10 ml. of water, giving 2.38 g. of white plates A, melting at 7680.5 C. Recrystallization of A from 25 ml. of methanol yields 1.25 g. of white plates B, melting at -87.5 C.

Analysis of B: Calculated for CmHsoOz: C, 75.55%; H, 11.88%; mol wt., 254.4. Found: C, 75.11, 75.38%; H, 11.88, 11.67%; mol. wt., 248, 248.

These results are in excellent agreement with the theoretical composition of a hexadecanedione.

' Example IX The process of Example V is carried out with 47.0 g. of l-carbethoxy-3,3,3-trifluoro2-hydroxypropyl-Z-hydroperoxide (prepared from ethyl trifluoroacetoacetate and hydrogen peroxide), a solution of 61.0 g. of ferrous sulfate heptahydrate dissolved in nitrogen-saturated distilled water to a volume of ml., and 60 ml. of liquid 1,3- butadiene. The reaction product, isolated as in Examples V and VI, amounts to 38.3 g. of a colorless oil. After removal of unreacted ethyl trifiuoroacetoacetate by distilla tion, there are obtained 2.9 g. of an intermediate fraction boiling from 83 C. to 141 C. at 1.8-2.0 mm., 7.7 g. of fraction 4 boiling at 145-146 C./1.5-2.0 mm., n 1.4488, and 8.1 g. of fraction 5 boiling at 148- 152 C./1.7 mm., n 1.4508. Fractions 4 and 5 comprise in major proportions the ethyl esters of butadiene dimers having carboxymethyl end groups.

A solution of 6.66 g. of fraction 4 in ethanol is hydrogenated at 30-40 lb./ sq. in. hydrogen pressure, using 0.1 g. of platinum oxide catalyst. Hydrolysis of the resultant hydrogenation mixture yields 2.5 g. of crude dodecanedioic acid melting at 104-'l09 C. Recrystallization of this crude acid yields pure 1,12-dodecanedioic acid, melting at.128.5- C. This pure acid when mixed with an authentic sample of 1,12-dodecanedioic acid'sho ws no depression in melting point.

Example X A solution of 66.0 g. (0.5 mole) of cyclohexanone peroxide in methanol (total volume 300 ml.) and a solution of 139 g. (0.5 mole) of ferrous sulfate heptahydrate in water (total volume 300 ml.) are added with vigorous agitation at equivalent rates to a solution of 86.1 g. (0.5 mole) of diethyl fumarate in 100 ml. of methanol over a 10-minute period at a temperature of 0 C. in an atmosphere of nitrogen. After one-half of the peroxide and ferrous sulfate solutions are added, a solution of 86.1 g. (0.5 mole) of ethyl fumarate in 100 m1. of methanol is added concurrently with the remainder of the other solutions. The reaction mixture is extracted with diethyl ether to remove the organic products, and the ether extracts are agitated with a solution of 55 g. of sodium carbonate in 500 ml. of water. The organic and aqueous layers are then separated. Acidification of the sodium carbonate extract yields 80.7 g. of a clear white oil which is believed to contain some 7,8,9,IO-tetracarbethoxyhexadecanedioic acid.

Analysis calculated for CzsHtsOrz: C, 58.5%; H, 8.0%; Sap. No., 95.7. Found: C, 56.98, 57.16%; H, 7.78, 7.74%; Sap. No., 151.1, 152.9.

Esterification of 50.0 g. of the crude product with 200 ml. of absolute ethanol using 1 m1. of concentrated sulfuric acid as catalyst yields 48.8 g. of crude ester. On molecular distillation of the crude ester there are obtained the following fractions:

Distillation and analytical data indicate that the crude esterified product is heterogeneous but is primarily the desired 1,6,7,8,9,14-hexacarbethoxytetradecane.

Example X] A mixture of 65.0 g. (0.5 mole) of ethyl acetoacetate and 62.2 g. (0.5 mole) of 27.4% aqueous hydrogen peroxide, and a solution of 139 g. (0.5 mole) of ferrous sulfate heptahydrate dissolved in water (total volume 200 ml.) are added with vigorous agitation at equivalent rates to a solution of 43.0 g. (0.5 mole) of vinyl acetate in 150 ml. of methanol over a period of minutes while the temperature is maintained at 0:15 C. After onehalf of the reactants have been added, an additional 43.1 g. (0.5 mole) of vinyl acetate is added concurrently with the remainder of the reactants. The product, isolated from the reaction mixture by ether extraction, is a pale yellow oil amounting to 69.8 g. This product is believed to contain diethyl 4,S-diacetoxyoctanedioate. The product yields the following fractions on distillation:

Fraction (No) B. P. Pressure Weight 111325 43-60 0 35-040 2.5 1. 4218 60110 0. 32-0. 35 a. 4 1. 4341 115-120 0. 2s 2. c 1. 4593 120-127 0 284135 1.1 1.4646 110-121 0 28 1.2 1. 4750 Analysis calculated for CraHzsOa: Sap. No., 86.6. Found; Fraction 3, Sap. No., 96.2, 91.3; Fraction 4, Sap. No., 92.4, 90.1.

It will be understood that the above examples are merely illustrative and that the present invention broadly comprises the process as hereinbefore defined. The invention also comprises, as new compounds, those longchain unsaturated alpha,omega-dicarboxylic acids having two nonconjugated ethylenic double bonds, as hereinbefore defined, and the esters of these acids with monohydric alcohols. For example, these dicarboxylic acids can be esterified by conventional methods with monohydric alcohols, e. g., methanol, ethanol, 1- and Z-butanol, and cyclohexanol.

The process of this invention is applicable to ketone peroxides generally, including peroxides of cyclic and acyclic ketones free of other functional groups, e. g., peroxides of monoand diketones, and of ketones having other functional groups, e. g., ketoesters, hydroxy ketones, and unsaturated ketones.

Specific acyclic ketone peroxides other than those used in the examples, well adapted for use in the process, include the peroxides of the 1,3-diketones, e. g., acetylacetone; of the 1,4-diketones, e. g., acctonylacetone; and ketoesters such as, for example, methyl trifiuoroacetoacetate, n-butyl oxomalonate, cyclohexyl acetoacetate, and n-dodecyl levulinate. The peroxides of ketoesters are especially useful in the process of this invention, and are, therefore, a preferred embodiment.

Specific cyclic ketone peroxides, other than cyclohexanone peroxide,,well adapted for use in the process, include the peroxides of cyclopentauone, 2-methy1cyclo pentanone, 2-, 3-, and 4-methylcyclohexanone, 2,4-dimethylcyclohexanone, cycloheptanone, cyclooctanone, cyclodecanone, cyclododecanone, cyclooctadecanone, and cycloeicosanone. Peroxides of cyclic kctones having 5 to 8 annular carbon atoms, inclusive, are also especially preferred in the process of this invention.

The ketone peroxides used in the instant process can be prepared by known methods. For example, the ketones canbe reacted with hydrogen peroxide as described in J. Am. Chem. Soc. 68, 533 (1946) and in U. S. Patent 2,298,405. They can also be prepared by other methods such as, for example, by treating a secondary alcohol, such as cyclohexanolor Z-butanol, with molecular oxygen, preferably in the presence of a free radical liberating initiator. For example, cyclohexanol can be treated with molecular oxygen at 60-85 C. using an azonitrile catalyst and adding calcium carbonate. Secondary alcohols can also be treated with molecular oxygen in the presence of ultraviolet light with or without the addition of benzoin or other photoinitiator.

It is not essential that the ketone peroxide be prepared and isolated before reacting it with the ethylenically unsaturated compound and the redox reducing agent. If desired, a mixture of the ketone and hydrogen peroxide can be added simultaneously with the other reactants.

Peroxides formed from cyclic ketones of the general formula occur, there must be indicated by the following formulas for cyclic ketone peroxides. 7

no OOH no -0 on (G) (C) n R a R r n Y R Some of the compounds represented by these formulas may be in equilibrium withothers with the relative proportions of each being dependent on the particular environment of the peroxide. A cycle ketone peroxides also exist in the same peroxide structures. In the reaction of this invention the ketone peroxides are believed to react in the form of the l-hydroxy-l-hydroperoxide, i. e., the structures and oon H HO\ /00 o and o R a a In addition to the specific unsaturated compounds illustrated in the examples, other polymerizable 1,3-conjugated dienes .or monoethylenically unsaturated aliphatic esters can be used in the process ofthis invention. Specific examples of suitable monoet'hylenically unsaturated aliphatic esters include dimethyl maleate and vinyl acetate. Specific examples of suitable 1,3-coniugated dienes,

include aliphatic and cycloaliphatic conjugatedv dienes, such as 1,3-cyclohexadiene, 1,3-pentadiene, 2,3-dimethyl- 1,3-butadiene, 2,3-dichloro-l,3-butadiene, 2-fiuoro-1,3- butadiene, and 2-phenyl-1,3-butadiene.

The specific compounds of the new class forming a part of this invention include, in addition to the dicarboxylic acids of the examples, 6,7,10,11-tetramethyl-6,10- hexadecadiene 1,16 dicarboxylic acid, 3,16-dimethyl- 7,1l-octadecadiene-l,l8-dicarboxylic acid, 9,10,13,14- tetrachloro-9,13-docosadiene-1,22-dicarboxylic acid, and 8,12-eicosadiene-1,ZO-dicarboxylic acid. Specific examples of esters of this invention include dimethyl 7,1l-octadecadiene-l,l8-dicarboxylate, diethyl 8,12-eicosadiene- 1,20-dicarboxylate, and dicyclohexyl 3,16-dimethyl-7,11- octadecadiene-l,16-dicarboxylate.

The redox reducing agents used in this invention are those reducing agents commonly employed in the redox art. The term redox is here used in its accepted sense to denote oxidation-reduction reactions in which an electron transfer occurs with the simultaneous formation of a free radical. In order for this free radical formation to present a substance which acts as the reducing agent for the peroxide compound, i. e., the peroxide of the ketone. Suitable redox reducing agents include the heavy metals capable of existing vinscveral valence states such as iron, cobalt, manganese, copper, chromium and the like, as well as l-ascorbic acid, sodium fonmaldehyde sulfoxylate, sodium bisulfite, the reducing sugars, and other reducing agents commonly used in the redox art.

The ketone peroxide and the reducing agent are preferably used in substantially stoichiometric proportions since a controlled degree of reduction is desired. Excess reducing agent tends to result in a decrease in the yield of desired addition product. The ethylenically unsaturated reactant is preferably used in excess of the amount stoichiometrically equivalent to the ketone peroxide being used, but is not used in excess of five moles of ethylenically unsaturated compound per mole of ketone peroxide. When less than one mole of unsaturated compound per mole of ketone peroxide is used, the direct coupling of two radicals from the peroxide tends to polymers of the unsaturate which then unite with terminal units derived from the ketone peroxide.

Instead of a stoichiometric amount of ferrous ion, the process of this invention can, if desired, be carried out with a trace of a multivalent metal such as, for example,

ferrous or ferric ion, together with another of the above-- mentioned reducing agents in an amount stoichiometrical- 1y. equivalent to the ketone peroxide, which serves to convert the ferric ion to ferrous ion as fast as the ferric ion is formed. In this type of process, the heavy metal may be thought as a promoter. Ferrous ion is preferred as such or as the promoter because of its efficiency and low cost.

Temperatures used in this process are not critical, and may vary over a wide range, depending on the particular reactants being employed. Temperatures of from C. to 100 C. or higher are operable. The temperature selected in any particular caseshould, of course, be below the decomposition temperature of any reactants being used and below the temperature at which undesirable side reactions take place. For example, when butadiene is used as the conjugated diene, it is preferred to use temperatures of about -20 C. in order to keep the volatile butadiene in pressure. with butadiene if the reaction is carried out in a closed container under pressure. Likewise, reaction temperatures below 0 C. are preferred when chloroprene is used, in order to minimize polymerization of this particular diene. The reaction time likewise is not critical. Generally, at least fifteen minutes are required for the complete addition of all the reactants and reaction times of about one hour give good results. However, longer times can be used if desired.

The dicarboxylic acids and esters of this invention are useful in many applications. They are especially useful as ingredients for the preparation of condensation polymers, for example, for condensation with difunctional alcohols and amines to form polyesters and polyamides. They are also useful as intermediates for the preparation of plasticizers and as surface-active agents. The presence of two nonconjugated ethylenic bonds in the dibasic acids and esters of this invention also render them useful as intermediates for reaction with compounds which add to double bonds. The diketones of this invention are useful as intermediates to long-chain dicarboxylic acids obtained by oxidation of the ketones and as intermediates to ligands formed by acetylation of the bis(methyl ketones).

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The invention claimed is:

1. Long-chain unsaturated alpha,omega-dicarboxylic acids and esters thereof, having two nonconjugated ethylenic double bonds, of the formula wherein R is from the group consisting of hydrogen, chlorine, and methyl, R is'an acyclic saturated hydrocarbon radical having a chain of 4 to 7 carbon atoms separating the carboxyl and (C4H4R2) groups, and R is from the group consisting of hydrogen and saturated hydrocarbon radicals of up to 6 carbon atoms.

2. 7,1l-octadecadiene-l,18-dicarboxylic acid.

'3. Process of preparing long-chain dicarbonyl compounds which comprises contacting a polymerizable ethylenically unsaturated compound selected from the group consisting of 1,3-conjugated dienes and monothe reaction system at atmospheric Of course, higher temperatures can be used ethylenically unsaturated aliphatic esters with a ketone peroxide selected from the group consisting of peroxides of cyclic ketones, peroxides of ketoesters and peroxides of acyclic diketones in the presence of a redox reducing agent, in a solvent for the reactants, the molar ratio of said ethylenically unsaturated compound to said ketone peroxide being from substantially 1:1 up to :1 to form a dicarbonyl compound consisting of a dimer of the ethylenically unsaturated compound coupled at each end to a carbonyl terminal unit from the ketone peroxide.

4. Process as set forth in claim 3 wherein said peroxide and said redox reducing agent are present in substantially stoichiometric proportions.

5. Process as set forth in claim 4 wherein said ethylenically unsaturated compound is a LII-conjugated diene.

6. Process as set forth in claim 4 wherein said peroxide is a peroxide of a cyclic ketone.

7. Process as set forth in claim 4 wherein said peroxide is a peroxide of a cyclic ketone having 5 to 8 annular carbon atoms, inclusive.

8. Process as set forth in claim 4 wherein said peroxide is a peroxide of a ketoester.

9. Process of preparing a long-chain unsaturated alpha, omega-dicarboxylic acid which comprises contacting a 1,3-conjugated diene with a peroxide of a cyclic ketone in the presence of a redox reducing agent, in a solvent for the reactants.

10. Process as set forth in claim 9 wherein said diene is present in a proportion of 1 to 5 moles per mole of peroxide, and said peroxide and said redox reducing agent are present in substantially stoichiometric proportions.

11. Process of preparing a long-chain unsaturated alpha,omega-dicarboxylic acid which comprises contacting 1,3-butadiene with a peroxide of a cyclic ketone in the presence of a redox reducing agent, in a solvent for the reactants.

12. Process as set forth in claim 11 wherein said butadiene is present in a proportion of 1 to 5 moles per mole of peroxide, and said peroxide and said redox reducing agent are present in substantially stoichiometric propor tions.

13. Process of preparing a long-chain unsaturated alpha,omega-dicarboxylic acid which comprises contacting 1,3-butadiene with cyclohexanone peroxide in the presence of a redox reducing agent, in a solvent for the reactants.

14. Process as set forth in claim 13 wherein said butadiene is present in a proportion of 1 to 5 moles per mole of peroxide and said peroxide and said redox reducing agent are present in substantially stoichiometric proportions.

15. Process as set forth in claim 14 wherein said redox reducing agent is ferrous sulfate and said solvent is aqueous methanol.

References Cited in the file of this patent UNITED STATES PATENTS 2,175,843 Kuhn et al Oct. 10, 1939 2,352,461 Walker June 27, 1944 2,360,673 Hanford Oct. 17, 1944 2,402,873 Cotfman et al. June 25, 1946 2,433,015 Roland et al. Dec. 23, 1947 2,433,016 Cotfman et al. Dec. 23, 1947 2,436,269 Scott Feb. 17, 1948 2,601,223 Roedel June 24, 1952 2,680,713 Lindsey et al June 8, 1954 OTHER REFERENCES Kuhn et al.: Beilstein (Handbuch, 4th ed.), vol. 2, p. 677 (1942). 

1. LONG-CHAIN UNSATURATED ALPHA,OMEGA-DICARBOXYLIC ACIDS AND ESTERS THEREOF, HAVING TWO NONCONJUGATED ETHYLENIC DOUBLE BONDS, OF THE FORMULA
 3. PROCESS OF PREPARING LONG-CHAIN DICARBONYL COMPOUNDS WHICH COMPRISES CONTACTING A POLYMERIZABLE ETHYLENICALLY UNSATURATED COMPOUND SELECTED FROM THE GROUP CONSISTING OF 1,3-CONJUGATED DIENES AND MONOETHYLENICALLY UNSATURATED ALIPHATIC ESTERS WITH A KETONE PEROXIDE SELECTED FROM THE GROUP CONSISTING OF PEROXIDES OF CYCLIC KETONES, PEROXIDES OF KETOESTERS AND PEROXIDES OF ACYCLIC DIKETONES IN THE PRESENCE OF A REDOX REDUCING AGENT, IN A SOLVENT FOR THE REACTANTS, THE MOLAR RATIO OF SAID ETHYLENICALLY UNSATURATED COMPOUND TO SAID KETONE PEROXIDE BEING FROM SUBSTANTIALLY 1:1 UP TO 5:1 TO FORM A DICARBONYL COMPOUND CONSISTING OF A DIMER OF THE ETHYLENICALLY UNSATURATED COMPOUND COUPLED AT EACH END TO A CARBONYL TERMINAL UNIT FROM THE KETONE PEROXIDE. 